Lap limiting fixture means



June 18, 1968 s. A. BOETTCHER LAP LIMITING FIXTURE MEANS 2 Sheets-Sheet 2 Filed Nov 16, 1964 United States Patent Office 3,388,506 Patented June 18, 1968 3,388,506 LAP LIMITING FIXTURE MEANS Stephen A. Boettcher, Deerfield, 11]., assignor t Speedlap Corporation, Skokie, Ill., a corporation of Illinois Filed Nov. 16, 1964, Ser. No. 411,225 16 Claims. (Cl. 51-129) My present invention relates to lap limiting fixture means for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc of a lapping machine.

The general type of lapping machine with which my present invention may be used includes a lapping disc, which is rotatably driven about a vertical axis, and on which truing and retaining rings rest. These rings, which are free to rotate on their own axes, serve to hold workpieces within them against movement with the lapping disc and to wear the lapping surface for maintaining it in planar condition. Arranged within the truing and retaining rings are weight or pressure plates that bear downwardly against the workpieces.

It is an object of my present invention to provide lap limiting fixture means for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate.

It is a further object of my present invention to provide lap limiting fixture means, as described, which is adapted to be used with existing standard forms of truing and retaining rings and pressure plates, without modification of the latter.

The lap limiting fixture means of my present invention, in general, is comprised of means which rests on the lapping disc within the truing and retaining ring and which is engageable by the pressure plate for arresting downward movement thereof. In one embodiment of my present invention, I provide an auxiliary ring which rests on the lapping disc within the truing and retaining ring and which carries adjustable stop means that is engageable by the pressure plate for arresting downward movement thereof. In another embodiment of my present invention, I provide a plurality of individual fixture components each having a horizontal base portion resting on the lapping disc and a vertical body portion with adjustable stop means carried thereby that is engageable by the pressure plate for arresting downward movement thereof. In a still further embodiment of my present invention, I provide means in the form of an auxiliary ring for holding fixture components of the type described in positive circumferentially spaced apart relation.

It is a further object of my present invention to provide lap limiting fixture means, as described, where-in the lower surface of the auxiliary ring that rests on the lapping disc, or the lower surfaces of the individual fixture components, as the case may be, are defined, at least in part, by wear resistant material. By reason of this construction, the bottom surfaces of the auxiliary ring or the fixture components are not subjected to wear during rotation of the lapping disc. Therefore, the distance between the bottom surfaces of the auxiliary ring or the individual fixture components and the top of the adjustable stop means remains constant for any particular setting, whereby to insure accuracy of lapping of workpieces with my lap limiting fixture means.

Now in order to acquaint those skilled in the art with the manner of constructing and using lap limiting fixture means in accordance with the principles of my present invention, I shall describe in connection with the accompanying drawings, preferred embodiments of my invention.

In the drawings:

FIGURE 1 is a partial elevational view, with portions being broken away and shown in section, of a typical lapping machine and one embodiment of lap limiting fixture means of my present invention;

FIGURE 2 is an enlarged fragmentary view, partly in section and partly in elevation, of the lapping machine and lap limiting fixture means shown in FIGURE 1;

FIGURE 3 is a plan view of the embodiment of lap limiting fixture means shown in FIGURES l and 2;

FIGURE 4 is a fragmentary sectional view of the lap limiting fixture means of FIGURE 3, taken substantially along the line 4-4 in FIGURE 3, looking in the direction indicated by the arrows;

FIGURE 5 is a fragmentary view, partly in section and partly. in elevation, of a modified embodiment of lap limiting fixtures means in operative position in a lapping machine;

FIGURE 6 is a sectional view of the lap limiting fixture means of FIGURE 5, taken substantially along the line 66 in FIGURE 5, looking in the direct-ion indicated by the arrows;

FIGURE 7 is a fragmentary view, partly in section and partly in elevation, of a further modified embodiment of lap limiting fixture means in operative position in a lapping machine; and

FIGURE 8 is a fragmentary sectional view of the lap limiting fixture means of FIGURE 7, taken substantially along the line 8-8 in FIGURE 7, looking the direction indicated by the arrows.

Referring now to FIGURE 1, there is indicated generally by the reference numeral 10 a typical lapping machine with which the lap limiting fixture means of my present invention maybe associated. The lapping machine 10 includes a framework with a tubular base or housing 12 which provides support for a horizontal lapping disc 14. By way of illustration, the lapping disc 14 may be of one-piece construction having a central well-bore 16 and a plurality of radial slots 18 for conveying across the disc abrasive and carrier mixture used in the lapping operation. Surrounding the lapping disc 14 is a staging table 20 from which workpieces can be moved onto the lapping surface of the lapping disc 14 and to which they can be returned when the lapping operation is completed. Selective rotation of the lapping disc 14 about a vertical axis is effected by drive means (not shown) mounted within the housing 12 and having an output shaft 22 connected to the underside of the lapping disc 14 by means of a hub member 24.

Suitably secured to the opposite sides of the housing 12 are the lower ends of vertical columns 26. Extending between the upper ends of the columns 26, above the lapping disc 14, is a horizontal bridge member 28 provided with four lateral arms 30, only two of which are shown. Each of the arms 30 has a vertical bore for receiving a vertically adjustable spindle 32 held in position by a set screw 34. The lower end of each spindle 32 is journalled in the center 'of a circular weight or pressure plate 36. The pressure plate 36 fit, with slight clearance, within truing and retaining rings 38 resting on the lapping disc 14.

Arranged within each of the truing and retaining rings 38 beneath the associated pressure plate 36 is the lap limiting fixture means of my present invention, one embodiment of which is identified generally by the reference numeral 44 in FIGURES l, 2, 3 and 4. The lap limiting fixture 44 comprises an auxiliary ring 46 having a bottom surface 48. Formed in the bottom surface 48 are circumferentially spaced apart generally rectangular recesses 50 which number three in the particular ring herein disclosed. Mounted or held in the recesses 50, as by an epoxy cement, are rectangular inserts or pad members 52 of wear resistant material such as boron carbide. The bottom surface 48 of the ring 46, and the lower coplanar faces of the pad members 52, are engageable with the lapping surface of the lapping disc 14. As shown in FIGURE 3, the ring 46 may be formed with suitable widened portions 54 to accommodate the pad members 52. The auxiliary ring 46 is also provided with a plurality of circumferentially spaced apart threaded vertical bores 56, preferably numbering three and being located centrally of the pad members 52. The ring 46 may still further be provided with upstanding boss portions 58 through which the bores 56 extend. Threadingly received in the bores 56 are the lower ends of vertical adjustable stop screws 66 adapted to be locked in predetermined positions by retaining nuts 62 arranged to be tightened against the top surface of the bosses 58.

After the fixture screws 60 have been vertically adjusted and locked in place, workpieces 64 and the fixture 44 are confined within the truing and retaining ring 38 and moved into position beneath the pressure plate 36. With the pressure plate 36 bearing against the workpieces, the heads of the screws 60 are initially spaced from the bottom surface of the pressure plate 36, and the amount of material that will be removed from the workpieces 64- is determined by the vertical distance between the lower surface of the pressure plate 36 and the heads of the fixture screws 60. Correspondingly, the ultimate vertical dimension of the workpieces 64 is determined by the vertical distance between the plane of the top surface of the heads of the screws 66 and the plane of the lower surface of the auxiliary ring 46.

As the lapping disc 14 is rotated, a freely flowing mixture of abrasive particles and an oil carrier is fed to the lapping disc 14 through a discharge tube 66 (FIGURE 1). A thin film of this abrasive mixture covers the lapping surface of the lapping disc 14, and during the lapping operation the truing and retaining ring 38, the auxiliary ring 46, and the workpieces 64 ride on such film. Also, during the lapping operation, the pressure plate 36 serves to impose a downward force or pressure on the workpieces 64 for increasing the rate of lapping of the latter; and the truing ring 38 rotates relative to the pressure plate 36 about the axis defined by the spindle 32 whereby to dress the lapping disc 14 for maintenance of its planar condition. As lapping of the workpieces 64 proceeds, the lower surface of the pressure plate 36 moves closer to the heads of the screws 60.

When the lower surface of the pressure plate 36 engages the top surfaces of the heads of the fixture screws 60, downward movement of the plate 36 is arrested and lapping of the workpieces 64 ceases automatically even though operation of the lapping machine continues. Because of the provision of the wear resistant pad members 52, the bottom surface of the auxiliary ring 46 is not subjected to wear during the lapping operation. Therefore, the vertical distance between the plane of the top surfaces of the heads of the fixture screws 60 and the plane of the lower surface of the auxiliary ring 48 remains constant in any adjusted position of the screws 60. As will be appreciated, a lap limiting fixture 44 may be arranged within each of the truing and retaining rings 38 on the lapping disc 14.

Referring now to FIGURES and 6, there is indicated generally by the reference numeral 68 at fixture component of a modified embodiment of lap limiting fixture means of my present invention. The fixture component 68 is comprised of a horizontal base portion 70 having a lower surface 71, and a vertical cylindrical body portion 72. The base portion 70 is formed with a longitudinal recess 74 in which is secured or held, as by an epoxy cement, a generally rectangular insert or pad member 76 of wear resistant material such as boron carbide. The bottom surface 71 of the base portion 70, and the lower coplanar face of the pad member 76, are engageable with the lapping surface of the lapping disc 14. Suitably formed in the vertical body portion 72 is a threaded opening 78 which threadingly receives the lower end of a vertically adjustable stop screw 80 adapted to be locked in predetermined positions by a retaining nut 82. At the time that workpieces are loaded within the confines of a truing and retaining ring 38, a plurality of pro-adjusted fixture components 68, preferably numbering three, are also disposed within the truing ring 38 at circumfcrentially spaced locations. The plurality of fixture components 63 thus located within the truing and retaining ring 38 function in the same manner as the lap limiting fixture means 44 to arrest downward movement of the pressure plate 36 whereby to automatically discontinue lapping of the workpieces upon completion of a predetermined amount of lapping.

Referring now to FIGURES 7 and 8, there is indicated generally by the reference numeral 86 a still further embodiment of lap limiting fixture means of my present invention. The lap limiting fixture means 86 comprises a plurality of fixture components 68, preferably numbering three, which are held or maintained in positive circumferentially spaced apart relation by means of an auxiliary ring 83. The ring 88 is provided with vertical bores 90 in which are threadingly secured the vertical body portions 72 of the fixture components 68. The lap limiting fixture means 86 functions in the same manner as the lap limiting fixture means 44.

It will be readily appreciated that any one of the abovedescribed embodiments of lap limiting fixture means of my present invention may be used with existing standard forms of truing and retaining rings and pressure plates, without modification of the latter.

While I have shown and described what I believe to be preferred embodiments of my present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of my invention.

I claim:

1. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, means independent of the pressure plate resting on the lapping disc within the truing and retaining ring and being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said last-named means coinciding with the desired. ultimate vertical extent of the workpieces.

2. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, means independent of the pressure plate having a lower surface resting on the lapping disc within the truing and retaining ring and having vertically adjustable stop means secured therein and engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said last-named means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

3. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of pad members resting on the lapping disc within the truing and retaining ring, means for holding said pad members, said holding means being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means coinciding with the desired ultimate vertical extent of the workpieces 4. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of wear resistant pad members resting on the lapping disc within the truing and retaining ring, means for holding said pad members, vertically adjustable stop means secured in said holding means and being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

5. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising an auxiliary ring resting on the lapping disc within the truing and retaining ring and being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means coinciding with the desired ultimate vertical extent of the workpieces.

6. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising an auxiliary ring resting on the lapping disc within the truing and retaining ring, a plurality of circurnferentially spaced apart vertically adjustable stop members secured in said auxiliary ring and being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

7. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising an auxiliary ring resting on the lapping disc Within the truing and retaining ring, said auxiliary ring havng circumferentially spaced apart recesses formed in the underside thereof, pad members of wear resistant material mounted within said recesses, vertically adjustable stop means secured in said auxiliary ring and being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

8. The lap limiting fixture means of claim 7 wherein said pad members are fabricated of boron carbide.

9. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of individual and independent fixture components resting on the lapping disc within the truing and retaining ring and being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means coinciding with the desired ultimate vertical extent of the workpieces.

10. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of individual and independent fixture components resting on the lapping disc within the truing and retaining ring, each of said fixture components having vertically adjustable stop means secured therein and engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

11. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of individual and independent fixture components within the truing and retaining ring, each of said fixture components having a horizontal base portion resting on the lapping disc and a vertical body portion with vertically adjustable stop means secured therein, said adjustable stop means being engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

12. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of individual and independent fixture components each having a pad member of wear resistant material resting on the lapping disc within the truing and retaining ring, each of said fixture components having vertically adjustable stop means secured therein and engageable by the lower surface of the pressure plate for arresting downward movement thereof, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

13. The lap limiting fixture means of claim 12 wherein said pad members are fabricated of boron carbide.

14. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and 'beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of fixture components resting on the lapping disc within the truing and retaining ring, said fixture components having vertically adjustable stop means secured therein and engageable by the lower surface of the pressure plate for arresting downward movement thereof, means for maintaining said fixture components in circumferentially spaced apart relation, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

15. The lap limiting fixture means of claim 14 wherein said last-named means comprises a ring.

16. For use in a lapping machine for predetermining the extent of lapping of workpieces positioned on a rotating lapping disc within a truing and retaining ring and beneath a pressure plate having a lower surface in a single plane engageable with the workpieces, lap limiting fixture means independent of the pressure plate comprising a plurality of fixture components within the truing and retaining ring, each of said fixture components having a horizontal base portion resting on the lapping disc and a vertical body portion with vertically adjustable stop means secured therein, said adjustable stop means being engageable by the lower surface of the pressure plate for arresting downward movement thereof, a ring having secured therein at circumferentially spaced apart points said verti- 7 cal body portions of said fixture components, and the overall vertical extent of said fixture means being adjustable to coincide with the desired ultimate vertical extent of the workpieces.

References Cited UNITED STATES PATENTS 2,565,590 8/1951 Bullard 51--131 Boettcher 51-131 Boettcher 51-131 Carter 51l31 X Emeis 51-131 Chapelle 51-131 X Boettcher 51131 HAROLD D. WHITEHEAD, Primary Examiner. 

1. FOR USE IN A LAPPING MACHINE FOR PREDETERMINING THE EXTENT OF LAPPING OF WORKPIECES POSITIONED ON A ROTATING LAPPING DISC WITHIN A TRUING AND RETAINING RING AND BENEATH A PRESSURE PLATE HAVING A LOWER SURFACE IN A SINGLE PLANE ENGAGEABLE WITH THE WORKPIECES, MEANS INDEPENDENT OF THE PRESSURE PLATE RESTING ON THE LAPPING DISC WITHIN THE TRUING AND RETAINING RING AND BEING ENGAGEABLE BY THE LOWER SURFACE OF THE PRESSURE PLATE FOR ARRESTING DOWNWARD MOVEMENT THEREOF, AND THE OVERALL VERTICAL EXTENT OF SAID LAST-NAMED MEANS COINCIDING WITH THE DESIRED ULTIMATE VERTICAL EXTENT OF THE WORKPIECES. 